Print Preview: Make print preview tab modal.

chrome/browser/resources/print_preview/print_header.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('print_preview', function() {
   'use strict';
 
   /**
    * Creates a PrintHeader object. This object encapsulates all the elements
    * and logic related to the top part of the left pane in print_preview.html.
@@ skipping 35 matching lines @@
       this.printButton_.onclick = this.onPrintButtonClicked_.bind(this);
       document.addEventListener(customEvents.UPDATE_SUMMARY,
                                 this.updateSummary_.bind(this));
       document.addEventListener(customEvents.UPDATE_PRINT_BUTTON,
                                 this.updatePrintButton_.bind(this));
       document.addEventListener(customEvents.PDF_GENERATION_ERROR,
                                 this.onPDFGenerationError_.bind(this));
     },
 
     /**
+     * Enables the cancel button and attaches its keydown event listener.
+     */
+    enableCancelButton: function() {
+      window.onkeydown = onKeyDown;
+      this.cancelButton_.disabled = false;
+    },
+
+    /**
      * Executes when a |customEvents.PDF_GENERATION_ERROR| event occurs.
      * @private
      */
     onPDFGenerationError_: function() {
       this.printButton_.disabled = true;
     },
 
     /**
      * Disables the cancel button and removes its keydown event listener.
      */
@@ skipping 87 matching lines @@
       // Removing extra spaces from within the string.
       html = html.replace(/\s{2,}/g, ' ');
       this.summary_.innerHTML = html;
     },
   };
 
   return {
     PrintHeader: PrintHeader,
   };
 });